Cables are omnipresent in all electrical systems, for the supply of power or transmission of information. These cables are subject to the same stresses as the systems that they connect and may be subject to failures. It is therefore necessary to be able to analyze their state and to return information on the detection of faults, but also on their location and their type, in order to help with maintenance. Conventional reflectometry methods allow this type of test to be carried out.
Reflectometry methods employ a principle that is close to that of radar: an electrical signal, the probe signal, often of high-frequency or wideband, is injected at one or more points into the cable to be tested. Said signal propagates through the cable or network and some of its energy is reflected when it encounters an electrical discontinuity. An electrical discontinuity may for example result from a connection, from the end of the cable or from a fault, or more generally from an abrupt change in the propagation conditions of the signal in the cable. Discontinuities most often result from faults that modify the characteristic impedance of the cable locally, thereby creating a discontinuity in its linear parameters.
The analysis of the reflected signals at the point of injection makes it possible to deduce therefrom information on the presence and location of these discontinuities, and therefore of any faults. An analysis in the time or frequency domain is conventionally carried out. These methods are designated by the acronyms TDR (for time-domain reflectometry) and FDR (for frequency-domain reflectometry).